1. Field of the Invention
The present invention relates to a scanning endoscope apparatus that can detect the position of a moving emission end of a fiber that is part of a scanning endoscope.
2. Description of the Related Art
Japanese Patent No. 3943927 discloses a scanning endoscope. In a general scanning endoscope, light for illumination is transmitted through an optical fiber from a stationary incident end to a movable emission end and a scanning operation is carried out by successively moving the emission end of the optical fiber.
It is necessary to recognize a position of the emission end of the optical fiber in order to produce an accurate image. However, it is difficult to mount a position sensor in an insertion tuba that contains and supports the emission end of the fiber because the diameter of the insertion tube is ideally kept as thin as possible. Accordingly, the position of the moving emission end cannot be accurately detected, and its position is estimated on the basis of a driving signal for controlling the movement of the emission end. However, the image that is produced may be distorted if the accuracy of the estimation is low.
An accurate image can also be produced when the emission end is moved precisely along a predetermined course. However, when the position of the emission end happens to move away from the predetermined course, its off-course position cannot be detected, making it difficult to return the off-course position to the correct course.